Doctors prescribe drugs known as CDK inhibitors to treat some women with estrogen-receptor-positive (ER+) metastatic breast cancer. Research into these drugs is ongoing, and new, promising CDK inhibitor options are on the horizon. Here, I address the current outlook for CDK inhibitors in ER+ breast cancer.

First, some background: ER+ breast cancers comprise about 70% of all breast cancers. The name reflects the fact that cells of these cancers express estrogen receptors (ERs), which are protein features targeted by many treatment strategies for this cancer type. The estrogen receptor (ER) protein is a treatment target not only because “it is there,” but mainly because it drives tumor cell proliferation in ER+ breast cancer. The activity of the ER depends on its binding to the hormone estrogen, and treatments known as endocrine drugs aim to prevent this interaction. Some endocrine drugs inhibit the synthesis of estrogen in the body (e.g., aromatase inhibitors, such as letrozole and anastrozole), and others prevent the interaction of estrogen with ERs (e.g., ER modulators such as tamoxifen, or the pure anti-estrogen drug fulvestrant). The problem of course is that, in metastatic breast cancer, resistance develops to each and every endocrine drug used. Continue reading…

“Brain metastases from primary breast cancer tumors often acquire clinically actionable genetic alterations, according to a small study. About one fifth of ERBB2/HER2-negative cases switched to HER2-positivity in the brain metastases.

” ‘Limited therapeutic options exist for patients with brain metastases,’ wrote study authors led by Nolan Priedigkeit, BS, of the University of Pittsburgh. ‘ERBB2/HER2-positive brain metastases have demonstrated encouraging responses to ERBB2/HER2-targeted therapies in recent clinical trials.’ ERBB2/HER2-negative brain metastases, however, have shown no such response.”

“The addition of a targeted agent to endocrine therapy for metastatic breast cancer led to unprecedented improvement in progression-free survival (PFS) that will have a ‘paradigm changing’ effect on clinical management, an investigator said here.

“Patients who received the cyclin-dependent kinase (CDK)4/6 inhibitor ribociclib in addition to letrozole (Femara) had a 44% reduction in the PFS hazard compared with patients treated with letrozole alone. The median PFS (primary endpoint) was 14.7 months with letrozole but had yet to be reached with letrozole plus ribociclib, ‘but it is expected to far exceed what the control arm did,’ Gabriel N. Hortobagyi, MD, reported at the European Society for Medical Oncology (ESMO) conference.”

“Adding a drug to a standard regimen for hormone receptor (HR)-positive and HER2-positive breast cancer improved progression-free survival, a researcher said here.

“In a Phase II randomized trial, investigators compared an aromatase inhibitor (AI) combined with pertuzumab (Perjeta) and trastuzumab (Herceptin) versus an AI just with trastuzumab in women with locally advanced or metastatic breast cancer, Grazia Arpino, MD, PhD, of the University of Naples Federico II in Italy, reported at a general session at the San Antonio Breast Cancer Symposium.

“The three-drug combination led to a median of 18.89 months without progression, compared with 15.8 months for the two drugs.”

“Breast cancer patients sometimes end up dying when their tumors spread all the way to the brain. Some very good drugs already exist for patients with breast cancer, especially ones with tumors that overexpress the HER2 marker, but that success has raised a new question: Can drugmakers take another step, and fight those deadly brain metastases that get people in the end?

“Seattle-based Cascadian Therapeutics is testing that idea this week with researchers gathered at the San Antonio Breast Cancer Symposium. Cascadian is reporting today that patients who got conventional capecitabine and trastuzumab, plus an experimental small-molecule drug, tucatinib (aka ONT-380), lived a median of 7.8 months without their tumors getting worse. About 61% of patients on that triple-drug combo saw tumors shrink. It’s an impressive result, given that these patients were especially ill when they enrolled in the study, having already received a median of three prior rounds of HER2-targeted therapy. The data are also holding up over time: a snapshot of the data from June showed patients living a median of 6.3 months without their tumors spreading.”

When it comes to the holiday season, Lori Wallace, a mother of two sons, is accustomed to being in charge. “I’m the mom, I’m kind of the epicenter of my family,” she says. “So I make Christmas.”

But in early April of 2011, Lori woke up with pain in her breast from what she thought was a small toy left in her bed by her five-year-old. No toy was there, and the pain persisted. She soon had her diagnosis: stage IIA invasive ductal carcinoma. Continue reading…